1. Field in the Industry
The present invention concerns a band pass filter for GHz-band used in the frequency range from hundreds of MHz to over ten GHz.
2. Prior Art
Nowadays, for familiar wireless communication devices radio waves of frequency range from hundreds of MHz to over ten GHz are preferably used. Examples are: 800 MHz (0.8 GHz) band or 1.5 GHz band for portable telephone (cellular phone), 1.9 GHz band for PHS, 5.8 GHz band for ETC (electronic toll collection system), 2.4 GHz band or 5.2 GHz band for wireless PAN, and 5.8 GHz band for DSRC (dedicated short range communication).
Because all the radio waves in these frequency ranges are used or possibly used in connection with driving or operating automobiles, it has been intended to utilize them all together by receiving with one antenna and by digital processing. In such cases or even in cases where the radio waves in each frequency ranges are used separately, a band pass filter which passes signals of a certain band width and cuts the other signals is required so that the data may be processed under elimination of noises caused by higher harmonics and reflected waves.
One of the assignees has developed and is providing various electromagnetic wave shielding materials which are made by dispersing soft magnetic powder in a matrix of a rubbery or plastic material. One of the inventors has invented and disclosed a low-pass (high-cut) filter using this electromagnetic wave-absorbing material (Japanese Patent Disclosure No. 2002-171104). The filter is of chip-type having a structure in which one signal line and at least one GND line of a conductive material run in parallel position in close contact on one surface or both the opposite surfaces of a rectangular sheet of a dielectric substance, and characterized in that an electromagnetic wave-absorbing material made by dispersing soft magnetic powder in a synthetic resin matrix is used as the dielectric substance. The product of the working example in the above disclosure has an insertion loss of −5 dB for high frequency waves higher than 1 GHz.